Electrical condenser



Sept. 21, 1948. c, L Y I 2,449,577 7 ELECTRICAL CONDENSER Filed Oct. 9,1942 I 2 Sheets-Sheet 1 CHRIS TOPHE]? E 6. BAILEY INVENTOR.

ATTORNEY Sept. 21, 1948. c. E. G. BAI Y 2,449,517

ELECTRICAL CONDENSER Filed Oct. 9, 1942 2 Sheets-Sheet 2 reamed Sept.21, 194s v were? I ELECTRICAL comansaa Christopher E. G. Bailey,Bournemouth, England, minor to Hartford National Bank and Trust Company,Hartford, Conn, as trustee,

Application october s, 1942, Serial No. 031,469

- In Great Britain mm 10, 1941 6 Claims. (Cl. 11541.5

to compensate for the changes which normally.

occur in the electrical constants or electrical oscillatory circuits dueto temperature changes of the components thereof and for this reason thecondensers are commonly referred to as compensating condensers.

It is an object of the invention to provide a compensating condenserhaving a variable temperature coeflicient of capacity value.

A further object of the invention is to provide a compensating condenserwhich is simple to manufacture and of low cost.

These and further objects of the invention will appear as thespecification progresses.

The invention will be further described with reference to the appendeddrawing forming part of the specification and in which Figure l is afront elevation in cross-section showing a compensating condenser inaccordance with-the invention.

Fig. 2 is a cross-sectional view of Fig. 1 alone the line 2--2.

Fig. 3 is a front elevation in cross-section showing a compensatingcondenser in accordance with another embodiment of the invention.

Figs. 4 to 8 show details of another emboditaken ment, of which:

Fig. 4 is a plan view,

Fig. 5 is a side elevation.

Fig. 6 is an elevation of one end,

Fig. 'l is an elevation of the other end,

Fig. 8 is a substantially central longitudinal section.

Referring to the drawing; the condenser shown in Figs. 1 and 2 comprisesa substantially c-shaped metal bracket it within which the electrodeelements of the condenserare contained. Bracket IO comprises a baseportion H, a supporting portion I! integral with the base Ii and an arml3 secured to the support II, for example, by a rivet it.

As one electrode of the condenser there is provided a metal plate orvane ll having a substantially semi-circular electrode portion l0 and anintegral arm ll extending at right angle to the portion I8 and by whichthe electrode is fixedly secured to the support I! by a rivet l8.

Positioned on an insulating shaft '20 and on opposite sides of theelectrode I! are substantially parallel semi-circular metal vanes ii-llforming the second electrode of the condenser.

Suitable materials for the base-support ii--l2, the am It, and vanes itand |8--l8 may be for example, brass Phosphor bronze or the like,whereas the shaft 20 consists of a material having a temperaturecoeillcient of linear expansion substantially diflerent from that ofsupport l2. For example, when using a support l: of brass, the shaft 20may consist of porcelain.

As shown, the vanes |8--l8 are arranged on diametrically opposite sidesof the shaft 20 whereby each vane 19 may be alternately brought incap'acitative relationship with the hired vane It by rotation the shaftIll as by means of a screw driver engaging a slot 22 formed at one endof the shaft.

For positioning the shaft 20 within the con denser assembly one endthereof is provided with an annular recess 24 which engages ofisetyokeportions 23-23 of the base i i said portions 23-21 serving as a thrustbearing for the shaft and preventing axial movement thereof relative tothe base. At its other end the shaft is flour-nailed.

through the arm I: which serves as a displacesble bearing for the shaftand permits unrestricted axial movement of the shaft relative to thearm. The condenser is secured to the apparatus of which it forms a part,for example, to a chassis 25 of a radio receiver, by rivets it-2tpassing through the base it and the chassis as.

The operation of the constant-capacity variable temperature coeiiiclentof capacity condenser of the invention is as follows:

Since the vanes 19-49 are arranged on dis.- metrically opposite sides ofthe shaft Ill, the

- capacity of the condenser remains substantially constant irrespectiveof the rotary position of the shaft 20 and correspondingly, irrespectiveof which the vanes I9 is adjacent to the vane it. However, due to thediflerential temperature expansion of the shaft 20 and the support I! achange in the temperature of the condenser produces a movement of theelectrode vane l5 relative to the vanes "-49 in a direction normal tothe planes of the vanes. This movement brings about either an increaseor a decrease in the capacity of the condenser'depending on thedirection of the temperature change and depending on which of thevanesI9 ,is positioned adjacent 'to the vane ii. For example, when thecondenser the capacity of the condenser. By reversing the position ofthe vanes I9I0 as by rotating the shaft 20 through 180 an increase intemperature decreases the spacing between the cooperating electrodes andbrings about an increase in the capacity of the condenser.

The temperature coeflicient ofthe capacity of the condenser can be givenany value between the positive and negative coeillcient limits of thecondenser by varying the degree of engagement of one or the other of thevanes I! with the vane I 0.

As will appear the limits of capacity coeillcient are determined by thearea of the electrodes vanes, and the spacing between the vanes, thedifferences in the temperature coefllcients of linear expansion of thesupport I2 and the shaft 20 and by the length of these members. Ingenera] the greater the area of the vanes, the greater the diiference inthe temperature coemcient of expansion of the materials of shaft 20 andsupport I2, thegreater the diiference in the temperature coefilcient ofexpansion of the materials of shaft 20 and support I 2, the greater thelength of these members, and the smaller the spacing between eachelectrode I9 and electrode IS the greater will be the limits of thevalue of capacity coefllcient.

The condenser shown in Fig. 3 comprises a substantially U-shaped metalbracket 30 having a III supported against the thrust plate of thebearing I00. Beyond the balls III the stem III has an increased diameterand is slidable in a bushing H2 in the end plate IIII. The outer endyoke portion 3| by which the condenser may be mounted, for example, onthe chassis 32 of a radio receiver, by means of rivets 82-42, and armportions 34-35 serving as supports for two fixed electrode vanes 38-30respectively. Electrode vanes 38-38 are secured to their respectivesupports by means of rivets 38-39 and are positioned in relativelparallel spaced planes.

The second electrode of the condenser consists of a metal vane 31secured to a rotatable shaft 4| and spacedly interposed between thevanes 38-38.

One end of the shaft 4| is fixedly bearinged in the yoke 3| in themanner previously described in connection with the condenser of Figs. 1and 2. The other end of the shaft 4| is journalled in displaceablebearings formed by the fixed vanes 3636 through which the shaft passes.

The materials constituting the supports 34--35 and the shaft 4| conformto the requirements previously set forth and a further description oithe same is believed to be unnecessary. The manner in which thecondenser is made to exhibit either a positive or a negative temperaturecoefiicient of capacity by rotation of the shaft 4| is also similar tothat of the condenser of Figs. 1 and 2.

Two end plates IOI, I02, made of porcelain for instance, are rigidlyunited by a metal structure consisting of bars I03 and a trough-likemetal screen I04 to which the bars I 03 are welded or otherwise secured.The metal structure I03, I04, which is suitably made of brass or othermetal of comparable coefllcient of expansion is attached to the endplates IOI, I02 by screws I08. A shaft I05 is rotatably supported in theend plates IOI, I02, being carried by a fixed thrust bearing I08, in theplate IN and an axially movable bearing I01 in the plate I02. The shaftI05 consists essentially of porcelain or other material of differentcoefilcient of expansion from the structure I03, I04. At the endadjacent the end plate IN the porcelain shaft I0! is mounted in a metalcollar I09 carrying a stem IIO of reduced diameter which passes betweenthe ball bearings of the stem H0 is slotted at II! to receive ascrewdriver or similar tool to facilitate rotation of the shaft I00. Theend of the porcelain shaft I00 adjacent the end plate I02 carries ametal collar II4 with a stem III on which two substantiallysemi-circular vanes I I0, I I! are secured so as to li on opposite sidesof the shaft I0! in parallel planes at right angles to the axis ofrotation or the shaft I05. The end of the stem II! abuts against bearingballs I I8 of the axially movable bearing I 01, the cylindrical block ofthe latter being axially slidable in a bushing II. in the end plate I02.A blade spring I 20 anchored tov the end plate I02 by one 01' the screwsI00 constantly urges the cylindrical block of the bearing I 01 inwardlyand thereby maintains the shalt I05 seating against the fixed thrustbearing I00.

Mounted on ,two arms I 22 secured to the end plate I 02 by rivets I24 isfixed substantially semicircular vane I24'which lies in a planeintermediate and parallel to the planes of the moving vanes I I8, I II.The vanes are of the same radius and are mounted so as to be concentricwith the shaft I00. The dimensions of the components of the condenserare so chosen that at a selected temperature the plane of the vane 24 isexactly halfway between the planes of the vanes I II, I I1. Then, atthis temperature, the capacity of the condenser is independent of therelative angular setting of the shaft I05 with reference to the fixedvane I24. However, variations in temperature will cause the fixed vaneI24 to approach one and to recede from the other of the movable vanesH6, H1. The resulting capacity variation will vary between a positiveand a negative maximum in accordance with the angular setting of theshaft I05, and thus the temperature coeiflcient of the condenser can bevaried arbitrarily between predetermined positive and negative limits.

A terminal tag I26 is connected to the fixed vane I24 by soldering toone of the rivets I22, while a terminal tag I2! is connected to themovable vanes I I6, I II, by frictional engagement with a shoulder I28integral with the metal stem IIB carrying these vanes. A terminal tagI29 is clamped by one of the screws I08 engaging the structure I03, I04,and is thereby electrically connected thereto. The structure I03, I04,can, if desired, be employed as an electrostatic screen.

It will be apparent that the condenser as illustrated can convenientlybe mounted behind a panel by anchoring means engaging the end plate I 0|an opening being provided in the panel for the passage of the stem I I0.On the face Of the panel, a scale and pointer can be provided toindicate the setting of the vanes I I6, II! in relation to the vane I24.

Instead of the disposition of the vanes as described and illustrated thetwo vanes may be stationarily carried by the framework consisting of theend plates and connecting structure, and the single vane may be carriedby the shaft.

If it is desired to augment the pressure at the thrust bearing I06 aspring washer may be interposed between the end plate I02 and theshoulder I20.

While I have described my invention by means of specific examples and inspecific embodiments. I do not wish to be limited thereto, for obviousmodifications will occur to those skilled in the art without departingfrom the spirit and scope of the invention.

I claim:

1. A temperature-responsive electrical condenser unit comprising a firstelectrode consisting of two substantially parallel metal vanes spacedlypositioned in staggered relationship with respect to each other inparallel noncoincident planes, a second electrode consisting of a metalvane spacedly interposed between the first vanes in a plane parallel tothe planes of said first vanes, a rotatable shaft member having one ofsaid electrodes secured thereto to alternately position one of saidfirst vanes and said second electrode adjacent one another, andtemperature-responsive means for moving one of said electrodes relativeto the other in a direction perpendicular to the planes of the vanes. 2.A temperature-responsive electrical condenser unit comprising a base, arotatable shaft member having one end axially fixed by said base, afirst electrode consisting of two substantially parrallel metal vanessecured to said shaft in spaced relationship and positioned ondiametrically opposite sides of the shaft in parallel noncoincidentplanes, a second electrode consisting of a metal vane positioned betweensaid first vanes in a plane between and parallel to the planes of saidfirst vanes, and a support interposed between the vane of said secondelectrode and said base, said rotatable shaft consisting of a materialhaving a coefficient of linear expansion different from that of thematerial of said support.

a 3. A temperature-responsive electrical condenser unit comprising abase; a rotatable shaft member having one end axially fixed by saidbase, a first electrode consisting of a metal vane secured to said shaftand extending radially therefrom, a

planes and having the major portion of theirsurfaces positioned ondiametrically opposite sides of the shaft, a supporting member securedto said base, a displaceable bearing journalled about the other end ofthe shaft and secured to said supporting member, a second electrodeconsisting of a metal vane secured to said supporting member andpositioned between said first vanes in a plane between and parallel'tothe planes thereof. said supporting member consisting of a materialhaving a coefficient of linear expansion different from that of thematerial of said shaft.

5. A temperature-responsive electrical condenser unit comprising arotatable shaft mounted at one end in a thrust bearing and supported atthe other end by a bearing permitting axial. movement and carried by arigid framework attached to the thrust bearing, a first electrodeconsisting of a pair of electrically connected vanes mounted in spacedparallel planes at right angles to the shaft on opposite sides thereof,a second electrode consisting of a fixed vane carried by the rigidframework in a plane parallel to and intermediate the planes of the pairof vanes, the coefficients of thermal expansion of the shaft and theframework being different so that the fixed vane, which is in a planemidway between the other two vanes at a selected temperature, moves inthe axial direction of the shaft with reference to the other vanes onchange of temperature.

6. A temperature-responsive electrical condenser unit as claimed inclaim 5 in which a metallic screening plate embraces the condenserelectrodes and forms part of the supporting structure theresecondelectrode consisting of two spaced metal vanes each lying in a separateplane parallel to the plane of said first vane and being positioned instaggered relationship on diametrically opposite sides of the shaft oneabove and one below the plane of said vane, supports securing the vanesof said second electrode to the base, said supports for.

CHRISTOPHER E. G. BAILEY.

REFERIEJN'CES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS

